Process for refining crude arsenic trioxide



SHAQG All@ 2i, ma.

C. L. RED

PROCESS FOR REFINING CRUDE ARSENIC TROXIDE v crude arsenic trioxide of high Patented ugo. 2d, 1923@ srarss Partnr or CHESTER Il). READ, F RAEWAY, NEW JERSEY,

Fics.

Lesiones.. ro AMERICAN SMELTING AND REFN ING GMPANY, GF NEW YORK, N.. Y., CBPORATION 0F NEW-JERSEY.

PItCESS FOR REFINING GRUDE ARSENIC TBIGXIDE.

Application le@ April 14,l 1923 Serial No. 102,090.

The invention relates to a process for refining crude arsenic trioxide and particularly antimony content. According to the invention there may be produced from crude arsenic trioxide of high antimony content a high grade arsenic trioxide practically free from antimony, which is known to the trade as high grade white arsenic and which may contain not less than 99% pure arsenic trioxide and `not more than 0.7% of antimony. l v

According to the invention crude arsenic trioxide commonly known as black dust which may be of high antimony content and which may contain other impurities, is treat-A ed in a refining furnace in anovel manner to produce pure high grade white arsenic,I ln the refining furnace thevolume of air and the temperatureparticularly near the lue is controlled so that glassy arsenic trioxide or vitreous arsenic is deposited in the iuc near the furnace. The remaining volatile crude arsenic trioxide passes over the vitreous arsenic which absorbs the antimony im uri-7 tion;

ties therefrom so that the arsenic trioXi e deposited further along the une is practically pure White crystalline arsenic trioxide.

In the drawings which illustrate a few forms of apparatus byv which the invention may be practiced: e v

Fig. l is a longitudinal section throu a rening furnace and' the flue thereof w ich maybe used to practice the invention, the

- due being modiied for practicing the invenllig. 2 is an enlarged longitudinal section through the due showing theconstruction of the baillcs fory the deposition of the vitreous arsenic trioxide, this section being taken on the line 2--2 of Fig., 3;

llig. 3 is a section` taken on the line 3-3 'of ll-ig. 2 showing the bao construction;

Fig t is a longitudinal sectionthrough the ue showing the construction of a modiied form of baille; and I Fig. 5 isa section taken along the line 5-5 of Fig.. 4L.

Referring now to the' drawing and more particularly to Figs.. l, 2 and 3, theWrefining furnace may' be a 'reverberateory furnace of any .desired construction having ahearth on which the charge of black dust or crude arsenic trioxide may be placed, and a fire box for supplying the necessary heatto run the furnace lhe lire box may have ay charge vvbe, divided into two sections.

i* lel tubes of alternate series may Y' of vtrioxide may be introduced.

Preferably spaced from the refining furnace proper is a liuc which may be generally rectangular in cross section and which may The rst section is the bao section or the section for the deposition ofthe vitreous oxide ofarsenic, and further along the fine is the section for the deposition of pure crystalline oxide .of arsenic and which is free from baiiies, this section being commonly known as the kitchen The liuc is connected to the furnace by a connecting pipe or flue 3 which may be of any construction. The connecting pipe and checker work or baille section of theiiue may be covered with a suitable layer of hea-t insulation ly to control the temperature of the fumes in the iiue.

'ln'one form of apparatus for practicing the invention the baille section may comprise series of baiiies each series comprising paralelongated members 5` extending across the flue, the members in alternate series being at right angles to each other. Fig. 3 shows two series of horizontal members anda se. ries of vertical members therebetween. These series may, however, be extended to include any number of alternate rows of balie plates desired. There should be a suitable number of battles to provide suiiicient area on which the vitreous oxide of arsenic may be deposited and without disturbing the iiow of gases too greatly.

Referring ynow tl'ernate baie which may comprise series of short tubes 6 whose axes are parallel to the longitudinal axisv of the fiue, the tubes in each series being piled one upon the other, as shown. The bslightly oiset to insure a good balde action. l' g It will be understood that the totalsurface the Fouilles which is available for'deposition of the vitreous oxide of arsenic will be controlled by the particular circumstances of the case, such as the character of crude ar- Y -senic trioxide, the kind of furnace, and the manner in which itis run, as well as the excellency of the desired product.

In operation, the temperature of the baille section or condensing portion of the flue near to Figs. 4 and 5, an al-l construction inay be provided I to be at a point slightly above the melting pointy of arsenic trioxide, so that. the arsenic #pipe and flue, and also by the temperature at trioxide which is condensed in this portion of the flue willpbe in the form 4of vitreous oxide of arsenic. The exact temperature will vary with conditions, but a temperature of 350 C. has been found suitable in practice.

The temperature may be. controlled bythe amount of insulation about the connecting which the furnace is operated which of course will depend on the rate at which the fuel is burned. The amount of air passing through the furnace and iue also may be used for controlling the temperature and is a very important factor for proper operation of the process. The temperature may also be controlled, if desired, by providing special external heating means at the section for the deposition of vitreous oxide of arsenic.

The best results have been obtained by maintaining the amount of air flowing through the refining furnace andflue at the minimum necessary to support combustion .of the fuel and also keep the furnace ata temperature suiiicient to volatilizeA arsenic trioxide at a commercially practicable rate. The volume of air is controlled by regulating the draft in the flue system and by taking special precautions to 'have the furnace and flue tight aga-inst the ingress 0f air except as may be necessary to admit air through the charging door for introducing and burning the fuel.

Another reason why the volume ofy air mustv be kept low is to allow a comparatively slow cooling of the vapors from the refiningl furnace as they pass through the iue in order toallow suiicient proportion of the arsenic trioxide vapors to deposit onthe bailes in the form of vitreous oxide of arsenic. Furthermore, the'antimony present which may be in theform of antimony oxide and which is sus-` pended in the vapor either in rthe form of vapors or as condensed solid particles, must be in contact withxthe vitreous oxide of arsenic a sutlicient length of time to be absorbed. It has beenfound that the antimoni7 content of the refined white arsenic decreases as the surface area of the vitreous oxide of arsenic is increased and as the volume of air iiowing through the furnace is decreased.

In practicing the invention under the conditions above pointed out, it has been found that the antimony oxides which are volatilized,

in the refining furnacey are absorbed by the vitreous oxide of arsenic to'an extent as high as 30% or more antimony in the vitreous oxide of arsenic. On the other hand 'the arsenic trioxide vapor whichcondenses further along the flue in the kitchen has been found to contain very little antimony and is a high grade white arsenic. By practicing the invention it has been found possible to recover 75% to of the arsenic troxide content in crude arsenic trioxide or black dust containing as high as 6% or more of antimony as high grade white arsenic containing less than 0.7% antimony.

Although a particular method of carrying out my improved process has been fully set forth, it is obvious "that various changes may be made in the process or in the separate steps -thcrcof without modifying or changing the essential features and characteristics of the product produced and that such product remains su` stantially the same although slight modiiications may be made itsappearance, texture and in its physical and chemical characteristics.

It will be understood that the apparatus disclosed may be changed and that other apparatus may be'used to practice the invention.

Although I have shown and described and have pointed out in the annexed claims vcertain novell features of the invention, it will be understood that various omissions, substitutions and changes in the/several steps of the process and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

Having described my invention, I claim 1. A process for refining crude arsenic trioxide comprising volatilizing the crude arsenic trioxide and passing the volatlized crude arsenic trioxide over a substancewhich will absorb impurities from the said crude arsenic triox'ide to produce pure white arsenic.

2. A process for refining crude arsenictrioxide comprising'volatilizing the crude arsenic trioxide and passingy the volatilized crude arsenic trioxide vover vitreous oxide of arsenic-which will absorb impurities from the crude. arsenic trioxide to produce pure white arsemc.

3. A process for refining crude arsenic trioxide having antimony as an impurity which comprises volatilizing the crude arsenic trioxide at such temperature that part thereof will condense in the form of vitreous oxide of arsenic, allowing the remainder of the volatilized crude arsenic to pass over the vitreous exideof arsenic, whereby the vitreous oxide of arsenic will absorb the antimony, and condensing the volatilized arsenic as pure white arsenic oxide.

4. A process for refining crude arsenic trioxide of high antimony content comprising heating the crude arsenic trioxide in alrefining furnace to volatilize the arsenic trioxide, conducting the vapors and gases from .the refining furnace through a section of flue for the condensation og'vitreous oxide of arsenic, so controlling the emperature of this section of flue and so controlling the volume of air flowing through the furnace and flue as to allow a portion of the arsenic trioxide vapor to condense as vitreous arsenic oxide and to allow a time ofcontact of the gases and vapors ill) from 'the refining' furnace with the vitreous arsenic oxide ample for the absorption of most of the antiniony, and condensing the purified arsenic trioXide vapor es high grade white arsenic in the remaining section of the Hue.. i

5. Aprocess 'of refining crude arsenic trioXide lia-ving antimony as an impurity, whichV comprises volatilizing thecrude arsenic trioxide in a furnace, exposing the fume of crude arsenic trioxide to vitreous arsenic oxide, controlling tlie air/through the furnace so as to allow the fume suiiicient time of contact with the vitreous arsenic oxide for the absorption of most of the antimony.

6. A process for removing antimonial coml ing it to vitreous arsenic oxide.

8. A process of separating arsenictrioxide from a mixture with antunony compounds, which comprises c'auslng a part of the arsenic vtrioxde to absorb the antimony and removing the remaining purified arse-nic trioxide.

In testimony whereof I have hereunto set my hand.

CHESTER L. READ. 

